The goal of this proposal is to further elucidate the function(s) of the short-chain and medium-chain carnitine acyltransferases that occur in mitochondria, endoplasmic reticulum, and peroxisomes of tissues such as liver. The working hypothesis for this research is: carnitine is involved in branched-chain amino acid metabolism. Carnitine octanyltransferase activity has been solubilized and purified to near homogeneity from beef heart mitochondria. This enzyme will be further purified and rigorously characterized. The effect of making the animals diabetic with streptozotocin will be investigated. Both changes in carnitine acyltransferase activity and acylcarnitines in liver and kidney of rats as well as other tissues will be studied. Studies will be performed on tissues obtained from alloxan-induced diabetes in sheep. The role of carnitine in the carnitine requiring yeast, Torulopsis bovina, will also be investigated. Studies on the oxidation of isobutyrylcarnitine by isolated mitochondria will also be completed. Soluble alpha-ketoisocaproate decarboxylase activity of various rat tissues will be investigated.